comparative study on atmospheric corrosivity of under

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American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) ISSN (Print) 2313-4410, ISSN (Online) 2313-4402

© Global Society of Scientific Research and Researchers

http://asrjetsjournal.org/

Comparative Study on Atmospheric Corrosivity of Under

Shelter Exposure in Yangon and Mandalay (Myanmar)

Yu Yu Kyi Wina*, Thinzar Khaingb, Zaw Min Htunc, Yasuo Suzukid, Kunitaro

Hashimotoe, Kunitomo Sugiuraf

aPh.D Candidate, Department of Civil Engineering, Yangon Technological University, Yangon, Myanmar b,cPh.D., Associate Professor, Department of Civil Engineering, Yangon Technological University,

Yangon, Myanmar dDr.Eng., Assistant Professor, Department of Civil and Earth Resources Engineering, Kyoto University,

Kyoto 615-8540 eDr.Eng., Associate Professor, Department of Civil Engineering,Kobe University, Kobe 657-8501

fPh.D., Professor, Department of Civil and Earth Resources Engineering, Kyoto University, Kyoto 615-8540 aEmail: [email protected]

bEmail: [email protected] cEmail: [email protected]

dEmail: [email protected] fEmail: [email protected]

Abstract

Corrosion is a degrading process and it is the main degradation problem in building industry around the world.

This study emphasises on the corrosivity classification of studied areas and discusses long term prediction for

thickness loss of carbon steel and weathering steel under shelter condition. Two locations, Yangon and

Mandalay, are selected as study areas in Myanmar. Corrosion rates are measured after one year exposure. The

pollutant data of sulphur dioxide and chloride deposition rates are measured according to JIS Z 2382 and the

meteorological data are collected by Easy USB data logger. The corrosion rate is classified based on ISO 9223

by evaluating the important atmospheric variables, such as time of wetness, CL- and SO2. The classes of sulphur

dioxide and chloride deposition rate can be seen low level for both areas and Time of Wetness (TOW) can be

seen τ4 for Yangon and τ3 for Mandalay.

------------------------------------------------------------------------

* Corresponding author.

http://asrjetsjournal.org/

American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2017) Volume 27, No 1, pp 386-404

387

So, according to ISO 9223, the corrosivity category for Yangon area is C3 and that for Mandalay area is C2-C3.

The actual mass loss for weathering steel is a little more than that of carbon steel in Yangon and adverse

condition can be seen in Mandalay after one year period. Then the future corrosion rates of studied areas are

discussed based on long time test results from JFE Steel Corporation, Japan. From this, weathering steel is

suitable when chloride deposition rate is less than or equal to 0.05 mdd because of its protective properties.

Keywords: Carbon steel and weathering steel; under shelter corrosion; ISO 9223 corrosivity classification.

1. Introduction

The great majority of people, corrosion mean rust, an almost universal object of hatred. Rust is, of course, the

name which has more recently been specifically reserved for the corrosion of iron, while corrosion is the

destructive phenomenon which affects almost all metals. Although iron was not the first metal used by man, it

has certainly been the most used, and must have been one of the first on which serious corrosion problems were

encountered [1]. Corrosion is often overlooked, but omnipresent phenomenon. It was estimated by the World

Corrosion Organization (WCO) in 2010 that 3% of the world’s GDP, $2.2 trillion was the annual direct cost of

corrosion worldwide [2].

The principle factors responsible for atmospheric corrosion of metal are temperature, gaseous pollutants, relative

humidity, rainfall, and wind velocity etc. Some of these effects are complicated on corrosion process, for

example, the increase of the temperature simulates the corrosion attack by enhancing the rate of electrochemical

and chemical reaction as well as diffusion process; moreover, the increase of temperature leads to more rapid

evaporation of the surface moisture films created by dew rain. Therefore, time of wetness is decreased by which

lower the corrosion rate [3]. Shelter exposure differs from unsheltered exposure in many ways. In the former,

the surface is shielded from direct precipitation and solar radiation. The shelter also prevents coarse aerosol

particles, such as windblown sea salt or soil dust, from reaching the corroded surface, at that time; it allows

interaction with smaller aerosol particles and gases. How these modifications of conditions influence the

corrosion process depends on the actual exposure conditions and varies from one case to another. Comparison of

long term exposure in the open and shelter conditions in the atmospheres with high air pollution (industrial,

marine) showed high corrosion rate of weathering steel in shelter conditions after longer exposures due to the

commutation of corrosion simulator on steel surfaces. In shelter conditions, the non-homogenous rust layer

formed which obtained higher concentration of corrosion stimulators (sulphates, chlorides) [4]. There is an

increasing trend of construction of steel structures in Myanmar because of their shorter construction time and

better resistance to earthquake than conventional reinforced concrete structures. However, the main problem of

steel structures is corrosion protection. But, there is no readily available record information about corrosion of

steel structures in Myanmar.

Therefore, it becomes an important problem to be considered about corrosion of structural steels in Myanmar.

This paper intends to classify the atmospheric corrosivity and to predict thickness loss for sheltered exposure of

urban area; Yangon and Mandalay in Myanmar.Yangon and Mandalay have high population because these are

the main commercial centers in Myanmar.


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2. ISO Classification of Corrosivity of Atmosphere

This standard is classified the corrosivity of an atmosphere based on measurement of time the wetness and

pollution categories (sulphur dioxide, airborne chloride). Based on these measures, an atmosphere is classified

as being one of five categories in terms of its corrosivity as shown in Table 1 [5].

Table 1: ISO 9223 Corrosion rates after one year of exposure predicted for different corrosivity classes

Corrosion Category Steel (g/m2/y) Copper (g/m2/y) Aluminum (g/m2/y) Zinc (g/m2/y)

C1 ≤10 ≤0.9 Negligible ≤0.7

C2 11-200 0.9-5 ≤ 0.6 0.7-5

C3 201-400 5-12 0.6-2 5-15

C4 401-650 12-25 2-5 15-30

C5 651-1500 25-50 5-10 30-60

Sulphur dioxide (SO2) is a colorless gas, belonging to the family of gases called sulphur oxides (SOx). It reacts

on the surface of a variety of airborne solid particles, is soluble in water and can be oxidized within airborne

water droplets. Sulphur dioxide, a product of the combustion of sulphur containing fossil fuels, plays an

important role in atmospheric corrosion in urban and industrial type atmospheres. It is adsorbed on metal

surfaces, has a high solubility in water and tends to form sulphuric acid (acid rain) in the presence of moisture

films. Sulfate ions are formed in the surface moisture layer by the oxidation of sulphur dioxide and their

formation is considered to be the main corrosion accelerating effect from sulphur dioxide. Sulphur dioxide may

be expressed either in terms of a deposition rate or an airborne concentration. The units used for the sulphur

dioxide categories in the ISO 9223 are as sulfate deposition (SD) rate in mg m-2 day-1 and it is shown in Table 2

[5].

Table 2: ISO 9223 classification of sulphur dioxide and chloride pollution levels

Sulphur Dioxide

Category

Sulphur Dioxide Deposition Rate

(mg/m2/d)

Chloride

Category

Sulphur Dioxide Deposition Rate

(mg/m2/d)

P0 ≤ 10 S0 ≤ 3

P1 11-35 S1 4-60

P2 36-80 S2 61-300

P3 81-200 S3 301-1500

Atmospheric salinity distinctly increases atmospheric corrosion rates. Apart from enhancing surface electrolyte

formation by hygroscopic action, direct participation of chloride ions in the electrochemical corrosion reactions

is likely. In ferrous alloys, iron chloride complexes tend to be unstable (soluble), resulting in further stimulation


389

of corrosive attack. Metals such as zinc and copper, whose chloride salts tend to be less soluble than those of

iron, generally display lower chloride induced corrosion rates. The initiation and propagation of localized

corrosion damage under the influence of chloride ions is most important. Pitting and crevice corrosion in

passivating alloys such as stainless steel, aluminum alloys or titanium are examples of such damage. The units

for the chloride categories (airborne salinity) in ISO 9223 are as chloride deposition (CD) rate in mg m-2 day-1

and it is shown in Table 2 [5]. From the fundamental theory, time of wetness (TOW) of a corroding surface is a

key parameter, which can directly determine the duration of the electrochemical corrosion process. This is a

complex variable, since all the means of formation and evaporation of the surface electrolyte solution must be

considered. The TOW refers to the period of time during which the atmospheric conditions are favorable for the

formation of a surface layer of moisture on a metal or alloy. For the purpose of the standard, this has been

defined as the time period during which the relative humidity is in excess of 80% and the temperature is above 0

degrees Celsius. TOW categories range from "Internal microclimates (τ1) with climatic control" to "Part of

damp climates, unventilated sheds in humid conditions (τ5) and it is shown in Table 3 [6].

Table 3: ISO 9223 classification of time of wetness

Wetness

Category

Time of Wetness (Percent) Time of Wetness

(Hours per Year)

Examples of Environment

τ1 <0.1 <10 Indoor with climatic control

τ2 0.1-3 10-250 Indoor without climatic control

τ3 3-30 250-2500 Outdoor in dry, cold climates

τ4 30-60 2500-5500 Outdoor in other climates

τ5 >60 >5500 Damp climates

Table 4: ISO 9223 corrosivity categories of atmosphere [6]

TOW CL- SO2 Steel Cu and Zn Al

τ 1 S0 or S1 P1 1 1 1

P2 1 1 1

P3 1-2 1 1

S2 P1 1 1 2

P2 1 1 2

P3 1-2 1-2 2-3

S3 P1 1-2 1 2

P2 1-2 1-2 2-3

P3 2 2 3

τ 2 S0 or S1 P1 1 1 1

P2 1-2 1-2 1-2

P3 2 2 3-4

http://corrosion-doctors.org/AtmCorros/TOW.htm#80%25

http://corrosion-doctors.org/AtmCorros/TOW.htm#No

http://corrosion-doctors.org/AtmCorros/TOW.htm#No


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Table 4: ISO 9223 corrosivity categories of atmosphere (Cont;)

TOW CL- SO2 Steel Cu and Zn Al

S2 P1 2 1-2 2-3

P2 2-3 2 3-4

P3 3 3 4

S3 P1 3-4 3 4

P2 3-4 3 4

P3 4 3-4 4

τ 3 S0 or S1 P1 2-3 3 3

P2 3-4 3 3

P3 4 3 3-4

S2 P1 3-4 3 3-4

P2 3-4 3-4 4

P3 4-5 3-4 4-5

S3 P1 4 3-4 4

P2 4-5 4 4-5

P3 5 4 5

τ 4 S0 or S1 P1 3 3 3

P2 4 3-4 3-4

P3 5 4-5 4-5

S2 P1 4 4 3-4

P2 4 4 4

P3 5 5 5

S3 P1 5 5 5

P2 5 5 5

P3 5 5 5

τ 5 S0 or S1 P1 3-4 3-4 4

P2 4-5 4-5 4-5

P3 5 5 5

S2 P1 5 5 5

P2 5 5 5

P3 5 5 5

S3 P1 5 5 5

P2 5 5 5

P3 5 5 5


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Table 4 shows classification of corrosivity of atmosphere based on ISO 9223.

3. Experiment

The corrosivity categories are defined by the one-year corrosion effects on standard specified in ISO 9223. The

corrosivity categories can be assessed in terms of the most significant atmospheric factors influencing the

corrosion of metals and alloys.

3.1. Test Sites

For this study, two stations, Yangon and Mandalay, were selected. The details at each site are described in Table

4 and the location of test sites are shown in Figure 1.

Table 4: Location of test sites

Environment Location Description

Urban Yangon Under the third floor ,Yangon Technological University, Yangon, Myanmar

Urban Mandalay Under the third floor , Mandalay Technological University, Mandalay,

Myanmar

Figure 1: location of test site


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Yangon is located in lower Myanmar at the convergence of the Yangon and Bago Rivers about 30 km away

from the Gulf of Martaban at 16°48' North, 96°09' East. It is a tropical monsoon climate under KÖppen climate

classification system. It is primary due to the heavy precipitation received during the rainy season that Yangon

falls under the tropical monsoon climate category [7].

Mandalay is located in upper Myanmar and it is a tropical wet and dry climate under KÖppen climate

classification system. Mandalay lies 21°58'30" North and 96°5'0" East [8].

3.2. Test Specimen Installation

Structural steel plates SM (carbon steel) and SMA (weathering steel) with dimension of 50mmx50mmx2mm

coupons were installed under the shelter of third floor at Yangon Technological University and Mandalay

Technological University. The location that the specimens installed are in open and free for air, facing with

wind direction.Exposure test was carried out under the shelter condition for 12 months, and corrosion loss was

measured after one year. The chemical compositions of selected structural steels supported by JFE are shown in

Table 6. Test specimen installation is shown in Figure 2.

Table 6: Chemical composition of selected structural steels

Material Chemical Composition (% by weight)

C Si Mn P S Cu Cr Ni Nb

SM 0.17 0.32 1.39 0.016 0.012 - - - -

SMA 0.12 0.39 0.9 0.008 0.006 0.36 0.61 0.22 0.014

(a) (b)

Figure 2: test specimen installation (a) Yangon (b) Mandalay

3.3. Collection of Atmospheric Variables

Meteorological data; such as temperature and humidity of locations, was recorded hourly by data logger. Time

of wetness (TOW) was calculated from the collected weathering data, based on ISO 9223.


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The pollutant data of chloride and sulphur dioxide were obtained by using dry gauze and lead dioxide cylinder

methodology, according to JIS Z 2382 [9]. The instruments were placed under the third floor of main building

of Yangon Technological University and Mandalay Technological University. They were collected one month

interval and determination of chloride and sulphur dioxide deposition rates were done by supporting Kyoto

University, Japan. The dry gauze method, JIS Z 2382 [9], was used for measuring the chloride deposition. This

method employs a dry gauze screen of 10cmx10cm gauze, which is chipped in hollow acrylic frame. After the

exposure, the chloride content was determined by Ion chromatograph method.

The sulphation cylinder method, JIS Z 2382 [9], was used for measuring the SO2 deposition. This method

employs a cylinder with a PbO2-coated gauze (100 cm2) wound around it for SO2 collection. Lead dioxide in

paste form was painted as a thin layer on a gauze cylinder and allowed to dry. This PbO2 reacts with SO2 of air

to form PbSO4. After the exposure, the lead peroxide layer was removed and the sulfate content was determined

by Barium sulfate precipitation method.

The collection of these environmental variables is shown in Figure 3.

Figure 3: collection of environmental variables (a) Yangon (b) Mandalay

3.4. Corrosion Rate Measurement

Corrosion rate may increase, or decrease, or remain constant with time. Quite often the initial attack is high and

then decreases.Thus, proper selection of time and number of exposure are important.

The exposure time was started at August, 2014 and after the completion of one year, identical three coupons for

each type was removed, cleaned, and weighted, which gives weight loss of that particular time interval.

Constructing an accurate corrosion prediction methodology requires the use of corrosion rate measurements

(weight loss per increment of time). Corrosion occurs at a rate determined by equilibrium between opposing

electrochemical reactions. Various methods are available for the determination of dissolution of metals in

corrosive environments but electrochemical employing polarization techniques are by far most widely used. The

corrosion rate (CR) is evaluated by mass loss method considering uniform corrosion after removal of corrosion


394

products. The corrosion rate is determined by the following Equation 1 as per standard, ISO 9226 [10].

rcorr = Δm/At (1)

In which, rcorris the corrosion rate, expressed in grams per square meter per year. Δm is the mass loss, expressed

in grams. A is the surface area, expressed in square meter and t is the exposure time, expressed in years.

4. Results and Discussion

Corrosivity classification for selected structural steels is determined based on ISO 9223 and then comparison

between estimated corrosion rates given by ISO 9223 and actual corrosion rates obtained from under shelter

exposures for two selected locations, Yangon and Mandalay.

4.1. Results for Corrosivity Classification Based on ISO 9223

The pollutant data of chloride and sulphur dioxide deposition rates for under shelter exposure for both Yangon

and Mandalay from March, 2014 to March, 2015 are shown in Figure 4 and Figure 5, respectively.

Figure 4: variation of chloride deposition rates for test sites

Figure 5: variation of sulphur dioxide deposition rates for test sites


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From figures, the chloride deposition rate for Yangon is higher than that for Mandalay. According to theory, the

closer the sea, the higher the chloride deposition rates. Yangon is near to the Gulf of Martaban and thus this can

cause higher chloride deposition rate than Mandalay.

The average chloride deposition rate for Yangon and Mandalay are 2.196 mg/m2/d and 1.43 mg/m2/d

respectively. According to ISO 9223, chloride class are S0 for both sites.

From sulphur dioxide deposition, Yangon is higher than Mandalay, in general. However, higher sulphur dioxide

deposition rates can be seen in Mandalay at April and May.

The average sulphur dioxide deposition rates are 1.242 mg/m2/d and 1.167 mg/m2/d for Yangon and Mandalay,

respectively. Therefore, according to ISO 9223, SO2 class for both sites is P0.

Figure 6: variation of temperature for test sites

The meteorological data, temperature, and relative humidity, for both Yangon and Mandalay from March, 2014

to March, 2015 are shown from Figure 6 and Figure 7, respectively.

Figure 7: variation of relative humidity for test sites


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From these figures, the temperature in Mandalay is relatively higher than that in Yangon although the relative

humidity in Mandalay has lower percentage than that in Yangon. The maximum relative humidity is over 90%

in Yangon when it is about 80% in Mandalay for the whole year.

Time of wetness is one of the important parameters that affect the corrosion rate. According to ISO 9223, time

of wetness can be calculated based on temperature and ralative humidity for each site, and the calculated values

are shown in Figure 8. The annual time of wetness in Yangon is much higher than that in Mandalay. In Yangon,

the annual time of wetness was 4002 hours and thus its class is τ4under ISO classification and in Mandalay, the

annual time of wetness was 1172 hours and thus its class is τ3 under ISO classification.

Figure 8: variation of time of wetness for test sites

Table 7: Classification of corrosivity class based on ISO 9223

Site SO2 CL- TOW Corrosivity

Class

Deposition Rate

(mg/m2/d)

Class Deposition Rate

(mg/m2/d)

Class Hours per

Year

Class Steel

Yangon 1.242 P0 2.196 S0 4002 τ4 C3

Mandalay 1.167 P0 1.43 S0 1172 τ3 C2-C3

In Table 7, the classes of sulphur dioxide and chloride deposition rate can be classified as low level and TOW

can be classified as τ4 in Yangon and τ3 in Mandalay. According to ISO 9223, τ4 can be found in outdoor

atmosphere in all climates (except for dry and cold climates); ventilated sheds in humid conditions; unventilated

sheds in temperate climate.

Yangon is the tropical monsoon climate and it has humid condition. Therefore, TOW is also high in Yangon


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than Mandalay. The corrosivity class of Yangon is C3 and that of Mandalay is C2-C3 and it is mainly due to

TOW class.

4.2. Results for Corrosion Rates

Corrosion rates and thickness losses for SM and SMA steel that are considered for under shelter condition after

one year exposure are shown in Table 8 and Figure 9.

Table8: Corrosion rates and thickness losses for SM and SMA steel

Site Corrosion Rate,g/m2/year

(Thickness losses,mm)

SM SMA

Yangon 25.68 (0.0033) 27.58 (0.0035)

Mandalay 10.50 (0.0013) 8.26 (0.0011)

Figure 9: corrosion loss (mm) for carbon and weathering steels

4.2.1. Relation Between Causes and Rate of Corrosion

As described in the previous section, the corrosivity class of Yangon is C3 and Mandalay is C2-C3. So, the

estimated corrosion rate for carbon steel in Yangon is 201-400 g/m2/y and that in Mandalay is 11-400 g/m2/year

according to ISO 9223. However, actual corrosion rate of carbon steel for Yangon is 25.68 g/m2/year and that

for Mandalay is 10.5 g/m2/year. So, the corrosivity classification of Yangon and Mandalay are both in C2 from

the view point of actual corrosion rate of carbon steels.

By comparing actual corrosion rates and estimated corrosion rates based on ISO 9223, it can be seen that actual

corrosion rates for carbon steel are much lower than estimated corrosion rates for under shelter exposure in both


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sites.

In Yangon, SMA has little higher corrosion rate than SM after one year of exposure because the protective layer

for weathering steel can form under the alternating wetting and drying cycle and this cycle cannot be formed

easily under shelter condition. According to literature, the longer exposure of sunlight seems to have resulted in

a more protective layer. The sunlight is so higher in Mandalay and it can help for formation of protective layer

to weathering steel and corrosion rate for SM steel is more than that for SMA steel.

Figure 10, Figure 11, and Figure 12 show the relation between thickness loss (mm) of SM steel and SMA steel

and chloride deposition rate (mdd), sulphur dioxide deposition rate (mdd), and distance from the sea (km)

respectively.

From these Figures, it can be clearly seen that thickness loss of SM steel is directly correlated with chloride

deposition rate and distance from the sea. However, the significant effect of sulfur dioxide deposition rate

cannot be seen on thickness loss of SM steel after one year of exposure.

Figure 10: relation between thickness loss of SM and SMA steels and chloride deposition rate

Figure 11: relation between thickness loss of SM and SMA steels and sulphur dioxide deposition rate


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Figure 12: relation between thickness loss of SM and SMA steels and distance from costal

4.2.2. Testing Result for carbon steel and weathering steel in Japan

This article discussed in relation between corrosion loss and chloride deposition rate for 1 year, 3 year, 5 year, 7

year, and 9 year exposure testing data tested in 40 locations, Japan supported by JFE steel cooperation. These

are considered as two conditions, chloride deposition rate is greater 0.05 mdd and less than or equal to 0.05

mdd.

Figure 13: relation between Thickness Loss of SM steel and chloride deposition rate (greater than 0.05mdd)

Figure 13 shows relation between thickness loss of SM steel and Chloride deposition rate and Figure 14 shows

relation between thickness loss of SMA steel and Chloride deposition rate (greater than 0.05mdd).


400

As shown in Table 9, the best correlation is found in 9 year exposure (correlation is 0.859 for SM and 0.882 for

SMA). From the correlation result, it is concluded that they have great influence in long duration. In conclusion,

it cannot be occurred the protective properties of SMA steel in the case of chloride deposition rate of greater

than 0.05 mdd due to higher chloride rate can destroy the protective properties of weathering steels.

Figure 14: relation between thickness loss of SMA steel and chloride deposition rate (greater than 0.05mdd)

Table 9: Correlation between thickness loss (mm) and chloride deposition rate (greater than 0.05mdd)

Exposure Year Pearson Correlation

SM 490 Steel SMA 490 Steel

1 year 0.804 0.874

3 year 0.681 0.843

5 year 0.768 0.578

7 year 0.788 0.849

9 year 0.859 0.882

Figure 15 shows relation between thickness loss of SM steel and chloride deposition rate and Figure 16 shows

relation between thickness loss of SMA steel and chloride deposition rate (less than or equal to 0.05mdd)

From Table 10, the best correlation can be seen in 3 year exposure (correlation is 0.880) for SM steel. The best

correlation can also be seen in 3 year exposure (correlation is 0.814) for SMA steel. The correlation is

decreasing after long time duration. In 9 year exposure, the correlation is only 0.561.Therefore, SM steel has


401

more chloride deposition effect than SMA steel for chloride deposition rate of less than or equal 0.05 mdd.

In conclusion, SMA steel is more suitable for the condition of chloride deposition rate of less than or equal 0.05

mdd because of protective properties of SMA steel.

Figure 15: relation between thickness loss of SM steel and chloride deposition rate (less than or equal to

0.05mdd)

Figure 16: relation between thickness loss of SMA steel and chloride deposition rate (less than or equal to

0.05mdd)


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Table 10: Correlation between thickness Loss (mm) and chloride deposition rate for SM and SMA Steels (less

than or equal to 0.05mdd)

Exposure Year Pearson Correlation

SM 490 Steel SMA 490 Steel

1 year 0.815 0.720

3 year 0.880 0.814

5 year 0.727 0.680

7 year 0.744 0.598

9 year 0.643 0.561

4.2.3. Discussion on future corrosion loss in Myanmar

Future corrosion loss for Yangon and Mandalay are predicted based on thelong-term data from JFE steel

cooperation tested in Japan and the one year data tested in Myanmar.

As shown in Figure 4, the chloride deposition rate for both Yangon and Mandalay is well under 5 mg/m2/d (0.05

mdd) and Mandalay area has lower chloride deposition rate than Yangon area. The average chloride deposition

rate for Yangon is 0.022 mdd and that for Mandalay is chloride deposition rate 0.014 mdd. Distance from the

sea of Yangon is about 59 km and that of Mandalay is 359 km. Therefore, the chloride deposition rate of

Mandalay is only about half for that of Yangon because the nearer the sea, the higher the chloride deposition

rate.

Thus the corrosion rate in Yangon is more than that in Mandalay. In Mandalay, the corrosion rate of SMA steel

is less than that of SM steel after one year of exposure.However the corrosion rate of SMA steel is a little more

than that of SM steel after one year exposure in Yangon. The chloride deposition rate in Yangon is only 0.022

mdd and thus it is well below 0.05. So, the protective properties of SMA steel will be occurred in longtime and

the corrosion rate will be decreased.

5. Conclusion

This paper emphasis on the corrosivity classification for under shelter corrosion of carbon steel (SM) and

weathering steel (SMA) in Myanmar (Yangon and Mandalay). The results are based on atmospheric variables,

such as pollutant and meteorological data and actual corrosion rate from one year results and discuss

oncorrosion rate for future is based on the results obtained from JFE steel Corporation, Japan.

The main conclusions of this paper are:

1. Average yearly sulphur and chloride deposition rate and time of wetness for Yangon is more than that


403

for Mandalay.

2. According to ISO 9223, the corrosivity class of Yangon is C3 and that of Mandalay is C2-C3.

3. From specimen exposure test, corrosion rate is lower in Mandalay than Yangon for carbon steel and

weathering steel.

4. Corrosion rate of carbon steel is more than that for weathering steel in Mandalay.

5. Converse condition can be seen in Yangon, where corrosion rate for weathering steel is more than that

for carbon steel.

6. The protective properties of SMA steel will be occurred in long time and the corrosion rate will be

decreased as chloride deposition rateis less than 0.05 mdd.

6. Recommendations

1 Long term test should be done for sheltered atmospheric exposure test to emphasize the influence of

atmospheric variables to structural steel

2 Unsheltered atmospheric exposure test should be done and compare with sheltered exposure test

3 Corrosion with laboratory testing should be studied and compare with atmospheric corrosion test result

Acknowledgements

First of all, the authors would like to sincerely thankful Dr. Nyan Myint Kyaw, Professor and Head of Civil

Engineering Department, Yangon Technological University for his kind lead and guidance. The authors would

like to offer special thanks to research group of “Corrosion and Deterioration of Construction Materials and

Strategic Maintenance of Infrastructures on Southeast Asia” and JFE Steel Corporation for their kindly help

throughout for research program. The authors would like to thank all the persons who have helped towards the

successful completion of this paper.

References

[1] Roberge PR, Handbook of Corrosion Engineering. The McGraw-Hill Companies, Inc; New York 2000.

[2] Hays, G.F.(2010)Now is the Time. World Corrosion Organization.

[3] N. B. S. Publication, Economic Effects of Metallic Corrosion in the United States, Publication No. 511,

National Bureau of Standard, Washington, DC (1987).

[4] Katsuhiko Asami and Michio Kikuchi, “Characteristics of Rust layers in weathering steels: Air-

exposed for a long period” Institute of Material Research, Tohoku University, Sendai 980-8577, Japan

[5] corrosion-doctors.org/AtmCorros/iso9223.htm

[6] ISO 9223: Corrosion of metals and alloys—corrosivity of atmospheres— classification.

[7] http://en.m.wikipedia.org/wiki/Yangaon


404

[8] http://en.m.wikipedia.org/wiki/Mandalay

[9] Japan Industrial Standard, JIS Z 2382, Determination of pollution for evaluation of corrosivity of

atmosphere.

[10] ISO 9226: Corrosion of metals and alloys—corrosivity of atmospheres— determination of corrosion

rate of standard specimens for the evaluation of corrosivity.

http://en.m.wikipedia.org/wiki/Mandalay

comparative study on atmospheric corrosivity of under

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